Home made block bells

[ikcdab]

I have made block bells before, but now I need some more!

This time the design is modified in as much as I have made proper tappers rather than the microswitch I used before. I have also aquired a 3d printer so have been able to make various components.

 

 

Above are bells, tapper, various mounts, bell pillars and solenoid cores.  Solenoids again wound from 0.65mm copper wire. The bells are out of old dial GPO phones. 

 

 

This is the "flap" mechanism that holds the bell tapper.

 

Here is the bell pillar.

 

 

Some partial assembly

 

 

 

Above are the various bits assembled for the first bell. And it works.

 

 

 

Next stage is the casing, and this is all in hand.

 

One question for the experts.  On the real things, were the bells adjustable "fore and aft" to get the correct contact between bell and clanger to get the right note? I worry that if I just glue them straight down, I won't be able to adjust them later, if needed.

 

Ian

Edited October 24, 2022 by ikcdab

[LNERGE]

It looks like you have made two coils that are simply acting as electro magnets to attract the armature. I'm in no doubt this will work but some effifiency may be gained by placing a steel yolk between the two cores at the oposite end to the moving armature. You may need to reverse the way the current flows through one of the coils if you try this.

 

There are various adjustments of differing styles available. I can post some pictures if required.

[RailWest]

1 hour ago, ikcdab said:

I have made block bells before, but now I need some more!

This time the design is modified in as much as I have made proper tappers rather than the microswitch I used before. I have also aquired a 3d printer so have been able to make various components.

 

 

Above are bells, tapper, various mounts, bell pillars and solenoid cores.  Solenoids again wound from 0.65mm copper wire. The bells are out of old dial GPO phones. 

 

 

This is the "flap" mechanism that holds the bell tapper.

 

Here is the bell pillar.

 

 

Some partial assembly

 

 

 

 

 

One question for the experts.  On the real things, were the bells adjustable "fore and aft" to get the correct contact between bell and clanger to get the right note? I Fraser that if I just glue them straight down, I won't be able to adjust them later, if needed.

 

Ian

Not exactly....

 

Have a look under the cover of one in a (WSR) signal-box convenient to you :-)

 

Usually there was some form of adjustable stop which limits the movement of the wide, flat armature piece. I don't know what the official guidance was - if indeed there was any - but I've found that the best result IMHO is to adjust it so that, when you push the armature slowly by hand, the 'striker' stops just short of the dome. When used 'in anger' there is sufficient momentum to carry the striker far enough further forward to strike the dome, but it then falls backs so as not to remain in contact with the dome and deaden the ring.

 

Also, by adjusting the padded 'back-stop' (horizontally threaded through the dome support pillar), you can adjust how far the striker has to move and that in turn affects how hard/soft it hits the dome.

[ikcdab]

2 hours ago, LNERGE said:

It looks like you have made two coils that are simply acting as electro magnets to attract the armature. I'm in no doubt this will work but some effifiency may be gained by placing a steel yolk between the two cores at the oposite end to the moving armature. You may need to reverse the way the current flows through one of the coils if you try this.

 

There are various adjustments of differing styles available. I can post some pictures if required.

Hi there thanks.  That sounds interesting, please could you explain more and post some pics.

Currently my two coils are wired in series.  I did wonder if wiring them in parallel or some other arrangement (maybe what you suggest) would be better.

 

Many thanks Ian

 

 

Edited October 24, 2022 by ikcdab

[RailWest]

I'll need to get into my store cupboards, it may take some time......

[ikcdab]

5 hours ago, LNERGE said:

It looks like you have made two coils that are simply acting as electro magnets to attract the armature. I'm in no doubt this will work but some effifiency may be gained by placing a steel yolk between the two cores at the oposite end to the moving armature. You may need to reverse the way the current flows through one of the coils if you try this.

 

There are various adjustments of differing styles available. I can post some pictures if required.

Having looked online i can now see what you mean. so its just a steel bar connecting the cores. What effect does this have? My steel cores are 6mm, so i can drill and tap them M3 and bolt a yoke across them. 

Ian

[St Enodoc]

20 hours ago, RailWest said:

I don't know what the official guidance was - if indeed there was any - but I've found that the best result IMHO is to adjust it so that, when you push the armature slowly by hand, the 'striker' stops just short of the dome. When used 'in anger' there is sufficient momentum to carry the striker far enough further forward to strike the dome, but it then falls backs so as not to remain in contact with the dome and deaden the ring.

That's exactly what Ray Hammond taught me over 50 years ago after I asked him about the bells on his Embridge layout. It works a treat.

[LNERGE]

23 hours ago, ikcdab said:

Having looked online i can now see what you mean. so its just a steel bar connecting the cores. What effect does this have? My steel cores are 6mm, so i can drill and tap them M3 and bolt a yoke across them. 

Ian

This will complete a magnetic circuit linking both coils. You will need to make sure your armature is not capable to touching the iron cores or it will latch up and stay put regardless of current flowing etc. 

 

 A residual pin is made from brass or copper in the end of each core stopping the armature touching the iron cores directly is essential. 
 

I hope to take some photos tomorrow but it is going to be a busy day. 

[LNERGE]

Have a look at this. Better than my ramblings.. The diagrams show the lines of force etc. 

 

http://www.samhallas.co.uk/repository/edu_pamphlets/ep_technical_electricity_1_1.pdf

Edited October 25, 2022 by LNERGE

[ikcdab]

11 hours ago, LNERGE said:

This will complete a magnetic circuit linking both coils. You will need to make sure your armature is not capable to touching the iron cores or it will latch up and stay put regardless of current flowing etc. 

 

 A residual pin is made from brass or copper in the end of each core stopping the armature touching the iron cores directly is essential. 
 

I hope to take some photos tomorrow but it is going to be a busy day. 

Thank you that's very helpful. I didn't know about the residual air gap, but by chance I have one. My iron cores are approx 0.5mm shorter than the 3d printed outer, so the armature does not contact the cores.  I hope the pic below shows it.

Does this look the part?

Ian

 

Edited October 26, 2022 by ikcdab

[LNERGE]

Freshly taken…

[ikcdab]

22 minutes ago, LNERGE said:

Freshly taken…

Excellent thank you.  What is the purpose of the second pair of coils? Do they break the circuit from the tapper in the other box so that you both can't send bell signals at the same time?

Ian

[LNERGE]

There is a relay attached to the bell line to the adjacent box. This relay operates the bell. Not required in your case I suspect.
 

The residual gap in your picture looks good. 

[uax6]

Another way of doing the residual gap is to drill the armature and insert a small set screw with a lock nut. You need to tap the armature and have the lock nut on the free side of the armature. You can then adjust the residual gap to get the optimum..

 

Richard, thats a rather nice bell unit...... older than ours here I guess.

 

Andy G 

Edited October 26, 2022 by uax6

[Michael Hodgson]

32 minutes ago, ikcdab said:

Excellent thank you.  What is the purpose of the second pair of coils? Do they break the circuit from the tapper in the other box so that you both can't send bell signals at the same time?

Ian

You are correct in saying you can't both send bell signals at the same instant, but that's because of the tapper circuit, not because of the relay.  The tapper is not a simple bell-push, it is like a morse key.  There is only one line wire for the bells, usually with return via earth - this being the most expensive part of the equipment (capital plus maintenance cost of miles of telegraph poles).

 

On a simple block bell (without relay), if you are not pressing your tapper, your bell is connected to the line wire, so your bell will sound in response to a voltage applied from the other end.  Pressing the tapper operates a break contact (tapper fully up under spring pressure), first disconnecting your own bell from the line wire, and then operating a make contact (the tapper fully down) which connects your battery to the line wire, operating the bell at the far end.  So you don't hear the bell signals you send on your own bell, all you hear in the box is the metallic clunk of the tapper.  Of course, unless a train is refused what you send is acknowledged by repetition , so the trainspotter outside on the platform generally does hear what signal was sent, but he actually hears only that response!

 

In the case of bells worked via relay, the relay rather than the bell itself receives incoming signals, powered by the battery at the remote end.  Your bell can then be run from a local battery.  This arrangement works better than the simple bell where several boxes can switch out of circuit at night, so the length of the line wire (and consequent voltage loss) varies according to which boxes are open.

[ikcdab]

On 24/10/2022 at 15:49, LNERGE said:

You may need to reverse the way the current flows through one of the coils if you try this

Just picking up on this one. My solenoids are laid out so that they match in polarity.  IE both both ends face the same way. So the armature contacts N and N.

Is that correct or should they be laid out such that the armature contacts a N and S pole? That would mean that the yoke at the opposite end would also be joined to a N/S.

Ian

[LNERGE]

27 minutes ago, ikcdab said:

Just picking up on this one. My solenoids are laid out so that they match in polarity.  IE both both ends face the same way. So the armature contacts N and N.

Is that correct or should they be laid out such that the armature contacts a N and S pole? That would mean that the yoke at the opposite end would also be joined to a N/S.

Ian

You’ll find they are opposing each other. Reverse the polarity of one and all should be well. 
 

For UAX6 the bell and block together 

[ikcdab]

44 minutes ago, LNERGE said:

1 hour ago, ikcdab said:

Expand  

You’ll find they are opposing each other. Reverse the polarity of one and all should be well. 

Thank you, I will reverse the polarity of one coil.  I had actually thought about this and assumed that I needed both coils to be oriented the same way, hence I have both norths at one end and both souths at the other.  But now you say it, I can see that it's rather like a set of AA batteries in a plastic holder. The + end of one is connected to the - end of the next and so the batteries lie "head to toe".  I'll alter my wiring and see what difference it makes.

Thanks again

Ian

 

 

[LNERGE]

IRSE green book No6 is a good read. It’s quite detailed regarding magnetic circuits. 
 

Dead impressed with what you’ve done so far

[ikcdab]

2 hours ago, LNERGE said:

Dead impressed with what you’ve done so far

Thank you.  Here is the first one with its casing.  I have made the bits for the second bell, just not assembled it yet.

Staining and varnishing next!

Ian

 

 

 

[Luke Piewalker]

Saw a layout at Cupar a couple of years ago that had two operators working with block bells and such. It took a turn when the two signallers had an argument about who was doing it right.

[LNERGE]

2 hours ago, ikcdab said:

Thank you.  Here is the first one with its casing.  I have made the bits for the second bell, just not assembled it yet.

Staining and varnishing next!

Ian

 

 

 

That looks magnificent. I’ll try and post something oddball tomorrow that’ll get you thinking. A crazy day today trying to do stuff between trains. A bit calmer tomorrow I hope. 

[ikcdab]

10 minutes ago, LNERGE said:

That looks magnificent. I’ll try and post something oddball tomorrow that’ll get you thinking. A crazy day today trying to do stuff between trains. A bit calmer tomorrow I hope. 

Thank you. I have been testing it with 12v, but i find that it works just as well on 5v so that is what I will probably use. The tapper contact is a brass stud onto a small brass plate, but with 12v i have been getting a bit of sparking and carbon (?) deposits. With 5v this is less, but i also might try swapping the contacts for nickle silver which might be better. 

Thanks again for your help

Ian C

[LNERGE]

Here’s the oddball relay.. I’m not suggesting you build one just posting for the fun of it..

 

This has three coils. Two are in series with the bell line between two signalboxes. The third coil is standing between the two coils and earth. 
 

When box A plunges the armature moves one way. When box B plunges it moves the other. One contact will operate a gong. The other a bell. When placed at an intermediate level crossing the keeper can determine the direction of the train from the bell codes etc. 

 

This one is going to be installed on a key token circuit over the winter. 

[ikcdab]

26 minutes ago, LNERGE said:

Here’s the oddball relay.. I’m not suggesting you build one just posting for the fun of it..

 

This has three coils. Two are in series with the bell line between two signalboxes. The third coil is standing between the two coils and earth. 
 

When box A plunges the armature moves one way. When box B plunges it moves the other. One contact will operate a gong. The other a bell. When placed at an intermediate level crossing the keeper can determine the direction of the train from the bell codes etc. 

 

This one is going to be installed on a key token circuit over the winter. 

Very nice, I don't need that on my model layout!  But I think we have something similar at watchet and Stogumber on the WSR.  There is a gong at those intermediate stations that is triggered when (I think) a token is released at either end.  I'm not sure exactly how it works, @RailWest will know more.

Ian